In vivo transfer of cholesterol from plasma into human aortic tissue

It has recently become possible to measure the in vivo flux of cholesteryl ester from plasma into human aortic tissue by use of labeled cholesterol in patients undergoing reconstructive aortic surgery. For the ascending thoracic aorta without visible atherosclerotic lesions the influx was 4.5 +/- 1.4 nmol X cm-2 X day-1 (means +/- SEM, n = 9). For the abdominal aorta with severe atherosclerosis the influx of cholesteryl ester was 45 +/- 5 nmol X cm-2 X day-1 (n = 12). In both types of tissues the influx of cholesteryl ester from HDL was 2-3 times higher than the influx of cholesteryl ester from LDL and VLDL compared with the concentration of these fractions in plasma. This is in accordance with an aortic influx-mechanism which depends on the sizes and the concentration of the lipoproteins in plasma. The transfer of plasma lipoproteins into human aortic tissue shows a number of similarities with the transfer of plasma lipoproteins into the aortic wall of cholesterol-fed rabbits and also with the transfer of other plasma macromolecules across various capillaries. The cholesterol content in intima-media tissue without lesions corresponded in some of the patients to less than one year of continuous influx of cholesteryl ester from plasma. This time is short compared with the age of the patients. It suggests that removal of cholesterol from the aortic wall represents a major importance in prevention of cholesterol accumulation in that tissue.